The presence of Listeria monocytogenes in Mozzarella di Bufala Campana (MBC) PDO cheese, recently notified at retail, suggested to revaluate the steps of cheese-making able to control the associated risk. While milk pasteurization is the usual CCP, the lethal effect of cheese curd stretching with boiling water should be better understood, as its management is aimed to obtain the typical fibrous cheese structure but microbial count reduction is only an expected and variable secondary effect. So, to predict the lethal effect of curd stretching according to the applied conditions by each dairy, the knowledge of the kinetic parameters of L. monocytogenes heat inactivation (Dt and z) in cheese curd becomes crucial. Similarly, knowledge of D and z of L. monocytogenes in tap water, brine and covering liquid will help to more efficiently manage the heat treatment of these fluids potentially contaminating MBC cheese surface after molding during the steps of cheese hardening, brining and packaging. Results obtained in the range from 60 to 70°C for times up to 30 min showed the relevance of the medium in determining a significant different heat resistance of L. monocytogenes. To increase the knowledge about mechanisms of post-contamination, the potential pathways of contamination among cheese and the fluids occurring after molding were studied, simulating different conditions. The ability of L. monocytogenes to be transferred from a contaminated fluid to the cheese surface, its adhesion and viceversa were demonstrated. Challenge tests performed at refrigerated temperature confirmed the inability of L. monocytogenes to grow within 30 d, but also its ability to survive. A possible competitive role of microflora transferred from MBC surface to covering liquid in controlling L. monocytogenes growth was evidenced. Heat treatment of all the fluids involved in MBC processing may be an important contribute to risk reduction
Management of Listeria monocytogenes risk during cheese-making and shelf life of Mozzarella di Bufala Campana PDO cheese / Ricci, Annalisa; Martelli, Francesco; Alinovi, Marcello; Garofalo, Alessandro; Mucchetti, Germano; Neviani, Erasmo; Bernini, Valentina. - ELETTRONICO. - (2020).
Management of Listeria monocytogenes risk during cheese-making and shelf life of Mozzarella di Bufala Campana PDO cheese
Annalisa Ricci;Francesco Martelli;Marcello Alinovi
;Germano Mucchetti;Erasmo Neviani;Valentina Bernini
2020-01-01
Abstract
The presence of Listeria monocytogenes in Mozzarella di Bufala Campana (MBC) PDO cheese, recently notified at retail, suggested to revaluate the steps of cheese-making able to control the associated risk. While milk pasteurization is the usual CCP, the lethal effect of cheese curd stretching with boiling water should be better understood, as its management is aimed to obtain the typical fibrous cheese structure but microbial count reduction is only an expected and variable secondary effect. So, to predict the lethal effect of curd stretching according to the applied conditions by each dairy, the knowledge of the kinetic parameters of L. monocytogenes heat inactivation (Dt and z) in cheese curd becomes crucial. Similarly, knowledge of D and z of L. monocytogenes in tap water, brine and covering liquid will help to more efficiently manage the heat treatment of these fluids potentially contaminating MBC cheese surface after molding during the steps of cheese hardening, brining and packaging. Results obtained in the range from 60 to 70°C for times up to 30 min showed the relevance of the medium in determining a significant different heat resistance of L. monocytogenes. To increase the knowledge about mechanisms of post-contamination, the potential pathways of contamination among cheese and the fluids occurring after molding were studied, simulating different conditions. The ability of L. monocytogenes to be transferred from a contaminated fluid to the cheese surface, its adhesion and viceversa were demonstrated. Challenge tests performed at refrigerated temperature confirmed the inability of L. monocytogenes to grow within 30 d, but also its ability to survive. A possible competitive role of microflora transferred from MBC surface to covering liquid in controlling L. monocytogenes growth was evidenced. Heat treatment of all the fluids involved in MBC processing may be an important contribute to risk reductionI documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
